Climate Change Blamed for Dead Trees in Africa

BERKELEY —Trees are dying in the Sahel, a region in Africa south of the Sahara Desert, and human-caused climate change is to blame, according to a new study led by a scientist at the University of California, Berkeley.

A dead ironwood tree (Prosopis africana) in Senegal, West Africa, is one of many trees that have died due to climate change. (Patrick Gonzalez photo)

“Rainfall in the Sahel has dropped 20-30 percent in the 20th century, the world’s most severe long-term drought since measurements from rainfall gauges began in the mid-1800s,” said study lead author Patrick Gonzalez, who conducted the study while he was a visiting scholar at UC Berkeley’s Center for Forestry. “Previous research already established climate change as the primary cause of the drought, which has overwhelmed the resilience of the trees.”

The study, which is scheduled for publication Friday, Dec. 16, in the Journal of Arid Environments, was based upon climate change records, aerial photos dating back to 1954, recent satellite images and old-fashioned footwork that included counting and measuring over 1,500 trees in the field. The researchers focused on six countries in the Sahel, from Senegal in West Africa to Chad in Central Africa, at sites where the average temperature warmed up by 0.8 degrees Celsius and rainfall fell as much as 48 percent.

They found that one in six trees died between 1954 and 2002. In addition, one in five tree species disappeared locally, and indigenous fruit and timber trees that require more moisture took the biggest hit. Hotter, drier conditions dominated population and soil factors in explaining tree mortality, the authors found. Their results indicate that climate change is shifting vegetation zones south toward moister areas.

“In the western U.S., climate change is leading to tree mortality by increasing the vulnerability of trees to bark beetles,” said Gonzalez, who is now the climate change scientist for the National Park Service. “In the Sahel, drying out of the soil directly kills trees. Tree dieback is occurring at the biome level. It’s not just one species that is dying; whole groups of species are dying out.”

The new findings put solid numbers behind the anecdotal observation of the decline of tree species in the Sahel.

Rainfall in the African Sahel declined more than anywhere else in the world in the period of recorded measurements, causing increased aridity, as evidenced by this dust storm in Senegal. (Patrick Gonzalez photo)

“People in the Sahel depend upon trees for their survival,” said Gonzalez. “Trees provide people with food, firewood, building materials and medicine. We in the U.S. and other industrialized nations have it in our power, with current technologies and practices, to avert more drastic impacts around the world by reducing our greenhouse gas emissions. Our local actions can have global consequences.”

– but they are still blaming climate which, although certain to drive trees to extinction eventually, isn’t the underlying reason they are dying so fast.

If it’s not more or less precipitation they have in common, what is behind this unmistakable trend, then? It seems only logical to ask, what do trees everywhere share in common?

The atmosphere!! Ozone precursors from burning fuel and other industrial processes are traveling around the globe, going in and out of complex chemical reactions. The persistant background level is inexorably rising. Scientists have been publishing research for decades indicating that ozone is toxic to vegetation.

I am afraid we have hit a tipping point where trees and other plants are suffocating in our pollution, either dying directly from exposure, or so weakened they are succumbing to secondary attacks by insects, disease and fungus. This increased vulnerability has been demonstrated in many controlled experiments, which have also shown that trees exposed to ozone are more likely to suffer damage from drought, wind and winter cold.

There is something quite peculiar about the reluctance of scientists, foresters, agronomists and government regulatory agencies to acknowledge what is rather obvious – we are killing the very species that are at the bottom of the food chain. Why wouldn’t they want people to understand this salient fact?

Organizations, such as California Rare Fruit Growers (http://www.crfg.org/) should be leading the effort to identify and propagate those trees which will be more compatible with the climate we are going to experience.

Gail Zawacki, I can’t be bothered to confirm whether you were actually banned from RealClimate, as you claim. However, whether you were or were not, the main reason for any disapproval expressed over there cannot possibly be any suggestions about models you may have made.

More likely, as a quick search for your name on RealClimate will reveal to anyone who cares to check, the disapproval stemmed from your totally out-of-control hysteria, complete with spitting profanity. If you weren’t banned, you certainly should have been given a reasonable timeout.

No Ric Merritt, the dispute began because supposedly, my suggestion that the loss of a carbon sink from dying trees was deemed “off topic” (and worse insults) for a climate change blog…because the trees weren’t dying.

Of course what you won’t find searching real climate are the very reasonable comments I made, indicating the validity of my observations that the trees are dying and the important connection to further increasing levels of CO2, that were thrown out in moderation.

We now know from multiple sources that I was correct. The trees are dying, it has been confirmed in numerous surveys.

You would think this would cause certain “experts” to reconsider their opinion of me, but I guess not.

Well, Gail, I’m with you. No trees-no people. Besides, I like trees, rather a lot. Some of my favourite people are trees. The problem is, surely, that we have (profanity) everything up, not just one or two biospheres or ecosystem but every (profanity)one. That is why we are (profanity).

No expert, I don’t have anything special to contribute about the underlying tree subject.

If you have anything valuable to say about it, you’ll reach the sizeable community of RealClimate readers, including me, better without the ^#&W)#$*&!. It’s the e-equivalent of shouting and spitting. In the particular episode discussed here, your contribution was the e-equivalent of shouting, spitting, throwing chairs through plate-glass windows, backing the car out of the driveway at quadruple speed without checking for neighborhood children, and running red lights at 80 MPH. Not nice. I avoid that stuff on line whenever possible, and stay away from the perpetrators.

The only reason I bothered to say anything here was to avoid groundless potshots at RealClimate, whose overall contribution far exceeds yours. If you think the opposite, you have a worse Galileo complex than I can help you with.

Ric, your elaborate and unwarranted personal attacks are exactly why I got angry at Real Climate. You (and the moderator there) refuse to discuss the merit of the subject I’ve brought up, and instead patronize and deride me. Those are denier tactics.

Thanks anyway, I don’t need your help with a Galileo complex. I’m concerned about trees. They need help.